Micro heat pipe with poligonal cross-section manufactured via extrusion or drawing

ABSTRACT

A micro heat pipe with a polygonal cross-section is manufactured via drawing. The micro heat pipe has flat or concave sides to allow working fluid to flow by capillary force generated at the edges of the micro heat pipe. Another micro heat pipe is manufactured by forming a plurality of through holes with a polygonal cross-section in a metal plate via extrusion, in which each of the through holes has flat or concave sides to allow working fluid to flow by capillary force generated at the edges of each of the through holes. The micro heat pipes can be manufactured easily via drawing or extrusion, can induce strong capillary force through simple structural modifications, and provide superior cooling effects.

BACKGROUND OF THE INVENTION

[0001] This application claims the priority of Korean Patent ApplicationNo. 2002-80869, filed on Dec. 17, 2002, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

[0002] 1. Field of the Invention

[0003] The present invention relates to a heat pipe, and moreparticularly, to a micro heat pipe for small, thin-film type electronicdevices.

[0004] 2. Description of the Related Art

[0005] With the advances of semiconductor manufacturing relatedtechnologies, chips packaged in electronic devices and systems havebecome smaller and have become more highly integrated. However, suchchips and systems generate a larger amount of heat per unit area, sothat effective cooling techniques are required. Specially, the latestsmall, thin-film type electronic devices require much smaller coolingdevices.

[0006] Conventionally, heat sinks, fans, small circular heat pipeshaving a diameter of 3 mm or greater, and the like have been used tocool small electronic devices. So far, heat sinks have been widely usedas basic cooling devices because their size and thickness can be easilyvaried in the manufacturing process. However, as the size of heat sinksis reduced more and more, the heat dissipating area becomes smaller andthe heat dissipating rate becomes lower. Meanwhile, fans have alimitation in that their size cannot be reduced unlimitedly. Inaddition, the fans are less reliable than other cooling devices.

[0007] A small heat pipe with a circular cross-section having a diameterof 3 mm or greater can be compressed to be suitable for a thin-film typestructure. However, when such a heat pipe is compressed, a wick thereofundergoes structural changes, and the heat transferring performance isgreatly deteriorated. Therefore, there is a need to manufacture a microheat pipe having a diameter of 3 mm or less for small, thin-film typeelectronic devices.

SUMMARY OF THE INVENTION

[0008] The present invention provides a micro heat pipe suitable forsmall, thin-film type electronic devices.

[0009] In accordance with an aspect of the present invention, there isprovided a micro heat pipe with a polygonal cross-section that ismanufactured via drawing and has flat or concave sides to allow workingfluid to flow by capillary force generated at the edges of the microheat pipe.

[0010] According to specific embodiments of the above micro heat pipe,the micro heat pipe may have at least one flat side. The polygonalcross-section of the micro heat pipe may be triangular or rectangular.Alternatively, a plurality of micro heat pipes with a polygonalcross-section are combined together in parallel to allow working fluidto flow by capillary force generated at the edges of each of the microheat pipes.

[0011] Another micro heat pipe according to the present invention ismanufactured by forming a plurality of through holes with a polygonalcross-section in a metal plate via extrusion, in which each of thethrough holes has flat or concave sides to allow working fluid to flowby capillary force generated at the edges of each of the through holes.

[0012] In this case, the through holes may have irregular sides. Thethrough holes may be interconnected in groups. The polygonalcross-section of the through holes may be triangular or rectangular.

[0013] The present invention also provides a micro heat pipe comprisinga plurality of micro heat pipes with a polygonal cross-section sealedwith a metal plate manufactured via extrusion, in which the plurality ofmicro heat pipes have flat or concave sides to allow working fluid toflow by capillary force generated at the edges of each of the throughholes. The plurality of micro heat pipes may have at least one flatside. The polygonal cross-section of the micro heat pipes may betriangular or rectangular.

[0014] As described above, a micro heat pipe according to the presentinvention can be manufactured easily via simple drawing or extrusion.The micro heat pipe according to the present invention can induce strongcapillary force through simple structural modifications, without need toinstall a separate wick for flowing working fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other features and advantages of the presentinvention will become more apparent by describing in detail exemplaryembodiments thereof with reference to the attached drawings in which:

[0016]FIGS. 1A through 1C are perspective views of micro heat pipeshaving a triangular cross-section according to an embodiment of thepresent invention;

[0017]FIGS. 2A through 2C are perspective views of micro heat pipeshaving a rectangular cross-section according to another embodiment ofthe present invention;

[0018]FIGS. 3A and 3B are perspective views of groups of micro heatpipes having a triangular or rectangular cross-section according toanother embodiment of the present invention;

[0019]FIGS. 4A through 4D are perspective views of multi-through holemicro heat pipes having a triangular or rectangular cross-sectionaccording to another embodiment of the present invention; and

[0020]FIG. 5 is a perspective view of sealed micro heat pipes having arectangular cross-section according to still another embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention will be described more fully with referenceto the accompanying drawings, in which exemplary embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as being limited to theembodiments set forth herein; rather, these embodiments are provide sothat this disclosure will be thorough and complete, and will fullyconvey the concept of the invention to those skilled in the art.

[0022] Referring to FIGS. 1A through 1C, which are perspective views ofmicro heat pipes having a triangular cross-section according to anembodiment of the present invention, the micro heat pipes aremanufactured via drawing. Working fluid is allowed to flow by capillaryforce generated at the edges 101, 111, and 121 of the micro heat pipesand a wick acting as a return path of the working fluid from a condensersection toward an evaporator section is not required. In other words, inthe micro heat pipes with a triangular cross-section according to thepresent invention, their sharp edges act as a wick.

[0023] In particular, the micro heat pipe of FIG. 1A with a triangularcross-section has three flat sides 100. The micro heat pipe of FIG. 1Bwith a triangular cross-section has three concave sides 110. The microheat pipe of FIG. 1C with a triangular cross-section has two concavesides 120 and one flat surface 130.

[0024] The micro heat pipes of FIGS. 1A through 1C may be made of metal,such as copper, easily via drawing. However, for the micro heat pipe ofFIG. 1A having the flat sides, the capillary radius is not small enoughto induce capillary force at its edges 101. To make the radius ofcurvature at the edges 101, 111, and 121 of the micro heat pipes assmall as possible, each side of the micro heat pipe may be concaved,like the sides 110 of the micro heat pipe in FIG. 1B.

[0025] When each side of the micro heat pipe with a triangularcross-section is made concave, a capillary force that is strong enoughto induce liquid flow can be generated due to the sharp edges 111.However, in order for the micro heat pipe to be easily and stably packedonto a surface of a target heat-generating source, it is preferable thatthe micro heat pipe is made to have at least one flat side, like theside 130 of the micro heat pipe in FIG. 1C.

[0026]FIGS. 2A through 2C are perspective views of micro heat pipes witha rectangular cross-section according to another embodiment of thepresent invention.

[0027] Like the micro heat pipes of FIGS. 1A through 1C, the micro heatpipes having a rectangular cross-section in FIGS. 2A through 2C aremanufactured via drawing. Working fluid is allowed to flow by capillaryforce generated at the edges 141, 151, and 161 of the micro heat pipesand a wick acting as a return path of the working fluid from a condensersection toward an evaporator section is not required. In other words, inthe micro heat pipes with a rectangular cross-section according to thepresent invention, their sharp edges act as a wick.

[0028] In particular, the micro heat pipe of FIG. 2A with a rectangularcross-section has four flat sides 140. The micro heat pipe of FIG. 2Bwith a rectangular cross-section has four concave sides 150. The microheat pipe of FIG. 2C with a rectangular cross-section has three concavesides 160 and one flat surface 170.

[0029] Although the capillary radius of the micro heat pipes with arectangular cross-section of FIGS. 2A through 2C is larger than thecapillary radius of the micro heat pipes with a triangular cross-sectionof FIGS. 1A through 1C, the micro heat pipes of FIGS. 2A through 2C canallow a larger amount of working fluid to flow because they have onemore edge 141, 155, or 161 acting as a flow pat of the working fluid.

[0030] In general, one or two micro heat pipes are mounted on a centralprocessing unit (CPU) of commercially available notebook computers. Thenumber of micro heat pipes to be mounted is determined by the internalchip-mount structure of the notebook computer and the cooling capacityof each micro heat pipe. However, if more compact electronic devicesproducing a greater amount of heat and having a thin-film typechip-mount structure is developed in the future, a wick-embedded heatpipe having a diameter of 3 mm or larger cannot be applied any longer.Accordingly, it is anticipated that a micro heat pipe with a triangularor rectangular cross-section that does not require a wick will soon bein demand.

[0031] Although the above-embodiments have been described with referenceto the micro heat pipes having a triangular or rectangularcross-section, a micro heat pipe according to the present invention mayhave any polygonal cross-section. It is also obvious that this conceptof the present invention utilizing a polygonal cross-sectional structurecan be applied to the micro heat pipes described bellows.

[0032]FIGS. 3A and 3B are perspective views of groups of micro heatpipes having a triangular or rectangular cross-section according toanother embodiment of the present invention. Reference numerals in FIGS.3A and 3B that are the same as those in FIGS. 1A through 1C and FIGS. 2Athrough 2C denote the same elements.

[0033] In particular, when there is a need to dissipate a larger amountof heat, the heat cannot be dissipated with only one of the micro heatpipes having a triangular or rectangular cross-section in FIGS. 1Athrough 1C and FIGS. 2A through 2C. In this case, as illustrated inFIGS. 3A and 3B, a plurality of micro heat pipes having a triangular orrectangular cross-section may be combined together in parallel toincrease the absolute heat transfer.

[0034] In FIG. 3A, a plurality of micro heat pipes of FIG. 1C arecombined together in parallel. Alternatively, a plurality of micro heatpipes of FIG. 1A or 1B may be combined together in parallel. Inaddition, a plurality of various micro heat pipes of FIGS. 1A through 1Cmay be combined together in parallel. In FIG. 3B, a plurality of microheat pipes of FIG. 2C are combined in parallel. Alternatively, aplurality of micro heat pipes of FIG. 2A or 2B may be combined togetherin parallel. In addition, a plurality of various micro heat pipes ofFIGS. 2A through 2C may be combined together in parallel.

[0035]FIGS. 4A through 4D are perspective views of multi-through holemicro heat pipes having a triangular or rectangular cross-sectionaccording to another embodiment of the present invention.

[0036] In particular, the micro heat pipes of FIGS. 4A through 4D aremanufactured from metal plates 200, 220, 240, and 260 via extrusion. Themetal plates 200, 220, 240, and 260 may be made of copper or aluminum. Aplurality of through holes 210, 230, 250, and 270 with a triangular orrectangular cross-section are formed in the respective metal plates 200,220, 240, and 260. The through holes 210, 230, 250, and 270 allowworking fluid to flow by capillary force generated at the edges 211,231, 251, and 271 thereof.

[0037] In particular, the micro heat pipe of FIG. 4A includes aplurality of through holes 210 with a triangular cross-section in themetal plate 200. Each side of the through holes 210 is concave towardoutside. It will be obvious that the through holes 210 may have flatsides. In addition, in order to minimize the space occupied by thethrough holes 210, the through holes 210 with a triangular cross-sectionmay be formed such that their apexes alternate in an upward and downwarddirection.

[0038] The micro heat pipe of FIG. 4B includes a plurality of throughholes 230 with a rectangular cross-section in the metal plate 220. Eachside of the through holes 230 is concave toward outside. It will beobvious that the through holes 230 may have flat sides.

[0039] The micro heat pipe of FIG. 4C includes a plurality of throughholes 250 with a polygonal cross-section, which is modified from therectangular cross-sectional structure of FIG. 4B, in the metal plate240. The through holes 250 with a polygonal cross-section have irregularsides.

[0040] The micro heat pipe of FIG. 4D includes a plurality of throughholes 270 with a polygonal cross-section, which are arranged in groupsof interconnected through holes, for example, two groups of threeinterconnected through holes, in the metal plate 260.

[0041]FIG. 5 is a perspective view of sealed micro heat pipes having arectangular cross-section according to still another embodiment of thepresent invention.

[0042] In particular, the sealed package of micro heat pipes of FIG. 5includes a metal plate 300. The metal plate 300 is made of copper oraluminum via extrusion. A plurality of micro heat pipes 310 having arectangular cross-section are closely arranged and sealed with the metalplate 30. In other words, the plurality of micro heat pipes 310 issealed exclusively with the metal plate 30. In the sealed package ofmicro heat pipes of FIG. 5, working fluid is allowed to flow bycapillary force generated at the edges of each of the micro heat pipes310.

[0043] Although the embodiment of FIG. 5 is illustrated with referenceto the micro heat pipes 310 with a rectangular cross-section, it will beobvious that micro heat pipes with any polygonal cross-section, forexample, a triangular or rectangular cross-section, as illustrated inFIGS. 1A through 1C and FIGS. 2A through 2C, may be sealed with such ametallic plate. In addition, the micro heat pipes with a polygonalcross-section sealed with the metal plate may have flat or concavesides. Alternatively, the micro heat pipes may have at least one flatside.

[0044] As described above, a micro heat pipe according to the presentinvention allows working fluid to flow by capillary force throughstructural modifications, without need to install a separate wick. Themicro heat pipe according to the present invention can be manufacturedeasily via drawing or extrusion with higher productivity. The micro heatpipe according to the present invention has a diameter as small as 3 mmor less and effective heat dissipating and heat transfer performance, sothat the micro heat pipe according to the present invention is quitesuitable as a cooling device for small, thin-film type electronicdevices.

[0045] While the present invention has been particularly shown anddescribed with reference to exemplary embodiments thereof, it will beunderstood by those of ordinary skill in the art that various changes inform and details may be made therein without departing from the spiritand scope of the present invention as defined by the following claims.

What is claimed is:
 1. A micro heat pipe with a polygonal cross-sectionthat is manufactured via drawing and has flat or concave sides to allowworking fluid to flow by capillary force generated at the edges of themicro heat pipe.
 2. The micro heat pipe of claim 1, having at least oneflat side.
 3. The micro heat pipe of claim 1, wherein the polygonalcross-section is triangular or rectangular.
 4. The micro heat pipe ofclaim 1, wherein a plurality of micro heat pipes with a polygonalcross-section are combined together in parallel, and working fluid isallowed to flow by capillary force generated at the edges of each of themicro heat pipes.
 5. A micro heat pipe manufactured by forming aplurality of through holes with a polygonal cross-section in a metalplate via extrusion, in which each of the through holes has flat orconcave sides to allow working fluid to flow by capillary forcegenerated at the edges of each of the through holes.
 6. The micro heatpipe of claim 5, wherein the through holes have irregular sides.
 7. Themicro heat pipe of claim 5, wherein the through holes are interconnectedin groups.
 8. The micro heat pipe of claim 5, wherein the polygonalcross-section of the through holes is triangular or rectangular.
 9. Amicro heat pipe comprising a plurality of micro heat pipes with apolygonal cross-section sealed with a metal plate manufactured viaextrusion, in which the plurality of micro heat pipes have flat orconcave sides to allow working fluid to flow by capillary forcegenerated at the edges of each of the through holes.
 10. The micro heatpipe of claim 9, wherein the plurality of micro heat pipes have at leastone flat side.
 11. The micro heat pipe of claim 9, wherein the polygonalcross-section of the micro heat pipes is triangular or rectangular.